The aim of the research is to clarify the essential nature and effects of manslaughter, to illustrate doctor's responsibility and liability in that regard, and to uncover new juristic developments relating to manslaughter and its applications in medical issues. The research consists of three chapters. The first is concerned with the facts of the new juristic developments as well as the essence of manslaughter, its forms and its consequences. The second is about medical responsibility, its causes, effects and nullifiers. The third is on contemporary applications of manslaughter in medical issues. The research findings have shown that manslaughter is essentially an accidental and unintentional killing of a human soul, and that doctors and their likes bear the responsibility of any of their actions resulting in such killing. This responsibility has certain causes, namely, acting contrary to principles of the medical profession, ignorance of the principles of the profession, error, treatment without permission of the patient or his guardian or the authority, and misleading. Each one of these causes has different legal effects. The research findings have also indicated cases of medical non-responsibility, specifically, those which involve certainty of the doctor's competence,-permission of the patient or his guardian, permission of the authority and doctor's non infringement. In addition, the findings have demonstrated that most of the actions of doctors and their likes resulting in killing are of the manslaughter kind. has put forward several Accordingly, the researcher recommendations, including: 1. Considering establishment of disciplined standards to distinguish medical errors from anything else. Y. The need for medical students and doctors to be instructed in medical ethics and be familiarized with ethical and professional medical responsibilities. T. Writing scientific studies and academic researches on several topics, including 'Siraya' (i.e. possible deadly effect of surgical removal of a body part on other parts) and its provisions in Islamic jurisprudence, custom and its impact and applications in the medical field, and cogency of the doctor's opinion in legal provisions.